Cutting through the coffee confusion

Jennifer Sygo, Postmedia News04.12.2012

As the second most commonly consumed beverage in the world (water is first, in case you are wondering; no, Captain Canada, it's not beer), to say that coffee is a global phenomenon is an understatement.

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Is coffee good for you? The question would have seemed a little ridiculous just a few years ago, but as evidence mounts that coffee drinkers are less likely to suffer from numerous chronic diseases, researchers are increasingly calling into question the belief that your morning cup of joe is a nutritional no-no. Let's take a closer look at the state of the evidence when it comes to this nutritionally enigmatic (yet wildly popular) beverage.

Coffee, health and disease

As the second most commonly consumed beverage in the world (water is first, in case you are wondering; no, Captain Canada, it’s not beer), to say that coffee is a global phenomenon is an understatement. Yet, despite its popularity, there exist long-held beliefs that caffeinated coffee is a) a diuretic (it’s not, as long as you consume it regularly), and b) bad for you, especially when it comes to your heart health.

Despite this perception, according to a number of population studies, most recently published in the April edition of the American Journal of Clinical Nutrition, even heavier coffee drinkers (usually defined as those who drink more than four cups — and we mean eight-ounce cups, not 20-ounce ventis — per day) are no more likely to develop heart disease than low-or non-consumers. And all of this is evident despite the fact that caffeinated coffee causes a blood pressure spike in the hours after its consumption, which suggests there is something more complex at work than caffeine’s impact on individual risk factors.

Similarly, while caffeine can cause a short-term spike in blood sugar, especially after a carbohydrate-rich meal (think coffee and a doughnut, or coffee and a bagel), an effect that is especially concerning for diabetics, population studies suggest those who consume four to six cups of coffee per day may actually be at a lower risk of type 2 diabetes.

And finally, while some components of coffee have been associated with the development of cancer cell lines, at least when studied in petri dishes or in animal models, when we compare coffee consumption and various types of cancer, we tend to see that coffee is not associated with cancer risk over a lifetime.

Cuppa calculations

Much of its controversy stems from the fact that, not only does coffee contain caffeine — in and of itself a challenge to study — but numerous compounds such as caffeic acid and magnesium, some of which act as antioxidants, while others improve blood pressure control or insulin sensitivity over time. Some of coffee’s benefits could also arise after habitual consumption: There is evidence our bodies adapt to coffee, and our metabolic response changes over time. Add to that the myriad ways to prepare coffee (drip, boiled, espresso, etc.), each of which affects coffee’s properties, and there are enough potential complicating factors to leave researchers with a headache that could rival a coffeelover’s in withdrawal.

And then there is the genetic factor: While most individuals are what we might call "fast caffeine metabolizers" — those whose bodies can readily break down caffeine into its byproducts — a segment of the population is genetically unable to produce CYP 1A2, the primary enzyme responsible for breaking down caffeine. These so-called "slow caffeine metabolizers" seem to be at a higher risk of developing heart disease when consuming what might otherwise be considered normal, or safe, amounts of caffeine. For slow metabolizers, caffeine intake in excess of 200 mg per day — the amount in about a cup-and-a-half of coffee, or about half of what Health Canada deems the safe upper intake level — may be enough to cause harm.

The bottom line

When it comes to understanding coffee, it’s clear we still have much to learn. As outlined in an editorial accompanying the recent American Journal of Clinical Nutrition study, while there is some good evidence it ight not be as harmful as once thought, and possibly even a bit good for us, we still need more research on the impact of caffeinated coffee on those with existing medical conditions, such as high blood pressure or type 2 diabetes. Also, while there is much research on the effects of filtered coffee on our health, there is less evidence on non-filtered coffee, which contains compounds that may harm our heart. Finally, while the authors of the population studies are able to control for numerous other risk factors, such as smoking or activity levels, in their analyses, there remains the possibility that coffee drinkers are healthier in some other, as-yet-undetected way, perhaps because of increased social interaction. Having said all of this, since there is evidence that decaf coffee is roughly on-par with its caffeinated counterpart when it comes to health benefits, consumers still have the luxury of choice — without having to stay up all night.

Visit Health Canada’s site for safe caffeine guidelines for different age groups: hc-sc.gc.ca. Jennifer Sygo is a registered dietitian at Cleveland Clinic Canada in Toronto.

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